The day was a stunner – warm sun, blue skies and no wind. A perfect day for setting things on fire (in a very controlled manner). We were very lucky to have Richard Self, an experienced biochar producer and author of biochar papers, leading the workshop.

First up we started a burn of wood pellets using a TLUD micro-kiln, made out of old Milo cans. While that was ticking along merrily we had a crash-course on soil science, and how biochar contributes to soil health. Biochar has vast surface area due to the presence of many microscopic pores. These pores make biochar a reservoir for water and nutrients, and provide a great habitat for beneficial soil microorganisms, where they can hide from predatory protozoa.

Left to right: One of our TLUDs; quenching the biochar, and paper cups: before and after. Photo credit Anna Kivi

Then it was into the nitty-gritty with biochar. Biochar the product of pyrolysing any organic material, from woodchips to dung. Pyrolysis is complex, but the key thing is that air flow is carefully restricted to the burning material – this results in the vast majority of the carbon in the organic material being retained, while pretty much everything else is burnt off – leaving you with relatively pure carbon with an awesome micro-structure. By contrast, when you burn wood on a normal fire (where oxygen flow is not restricted), all the carbon in the wood is turned into carbon dioxide, and the ash that remains consists of silicates, calcium carbonate and very alkaline potassium hydroxide.

So in summary, burying biochar in soil greatly improves soil fertility, while sequestering carbon underground for many years (potentially thousands), preventing it from entering our atmospheres as climate enemy CO2. What an epic win-win.

Without further ado, we proceeded to burn more stuff. We tried the Kon-tiki method (no, we didn’t burn a busload of partying youths) adapted for a metal wastepaper bin – I was pleasantly surprised at how simple this was. Next we got electric drill trigger-happy and built our own tin-can TLUDs. With the TLUDs, we experimented with making biochar from paper cups from the Hospital staff kitchens (we intend to work with the Hospital to help reduce this large waste stream of theirs). To our delight, it worked like a charm. To quench all the biochar we made, we used a homemade seaweed tea, to load the pores with nutrients.

Everyone went home with slightly sooty hands and the grins of people who have learnt a brilliant trick, which is sustainable, cheap and helps us grow better food while improving the planet for generations to come. Next, we will be doing experiments to see how our biochar affects plant growth, and organising another workshop that will be open to the public: watch this space! We might even toast some vegan marshmallows on the kilns next time.

Left to right: using the Kon-tiki method with cardboard; how’s that for a workshop setting; and some finished biochar. Photo credit Anna Kivi

Written by Kate Daniell, the Compost Queen of workerBe oasis inc. soc.

With Permaculture Design in your garden you will…

+ get higher yields for less time and energy
+ let nature do a fair part of the work
+ get more food out of smaller spaces
+ make your soil more fertile for each season
+ invite beneficial wildlife
+ have nutritious fresh food, year round